Fired heater for high control sensitivity service



June 2, 1964 J. J. GRIFFIN 3,135,247

FIRED HEATER FOR HIGH CONTROL SENSITIVITY SERVICE Filed March 21, 1962 '2 Sheets-Sheet 1 @WWAE N 32 zwmg 3 wmm: 28 @wmw l I //v VENTO/Q 1 JbH/v J GRIFFIN.

ATTORNKY J. J. GRIFFIN June 2, 1964 FIRED HEATER FOR HIGH CONTROL SENSITIVITY SERVICE 2 Sheets-$heet 2 Filed March 21, 1962 awn 70R JOHN J. GE/FF/N BY A 7' TOR/V5 Y United States Patent 3,135,247 FIRED HEATER FGR HIGH CONTROL SENSITIVITY SERVICE John J. Grifiin, Huntington, N.Y., assignor to Foster Wheeler Corporation, New York, N.Y., a corporation of New York Filed Mar. 21, 1962, Ser. No. 181,363 2 Claims. (Cl. 122-356) This invention relates to a fired heater of high control sensitivity and suitable for example in heating cryogenic 1 air is introduced via the entrance chamber in counterflow relationship with the combustion gases in the inner shell so that the inner shell is cooled as the combustion supporting gas is preheated.

Gas cooling accommodates the use of a thin inner shell which does not storeheat and, accordingly, permit rapid response to heat input to flame control.

7, Another advantage of this design is improved lateral distribution of heat occasioned by the injection of tertiary combustion supporting gas.

These and other advantages will appear more fully from the accompanying drawings of a gas cooled fired heater embodying this invention and wherein:

FIGURE I is an elevational view in cross section taken along line II of FIGURE II.

FIGURE 11 is a side elevational view partly in cross section taken along line II-II of FIGURE I.

Elongated thin inner shell 1 is supported in spaced relationship relative outer shell 2. The first extent of inner shell 1 is'shown as bottom 3. The second extent is shown as top 4. Inner shell 1 also has sides 6 and ends 7 defining combustion chamber 8 with upper zone 9 and lower zone 11. Sides 6 converge toward bottom 3 so that lower zone 11 opens upward. In most cases it would be desirable to fabricate inner shell 1 from a heat resistant metal such as a nickel-chromium alloy steel or a nickel alloy cast iron.

Elongated outer shell 2 has sides 12, ends 13 and a second or upper extremity 14. Outer shell 2 encloses entrance chamber 16 which embraces inner shell 1.

Heaters of this type are preferably fired by a gaseous fuel. Burner means, generally designated 17, include burner nozzles 18 which penetrate inner shell 1 at the first extent via bottom opening 19 thereof. Flue means shown as stack 20 are located in the vicinity of top 4 so that flame is coursed upward through combustion chamber 8. Burner nozzles 18 communicate via conduits 21 with a source of fuel (not shown). Means shown as burner block 22 with inner opening 23 are mounted about each burner nozzle 18 and communicate with entrance chamber 16 to introduce combustion supporting primary gas to mix with the fuel as it enters the combustion chamber.

Burner blocks 22 are spaced from bottom lip 24 of inner shell 1 so as to define outer openings 26 for the admission of secondary combustion supporting gas from entrance chamber 16 to further support combustion.

Inner shell 1 also defines a plurality of tertiary ports 27 communicating entrance chamber 16 with lower zone 11 to introduce tertiary combustion supporting gas into ice.

combustion'chamber 8. -It is usually desirable to introduce about ten percent of the combustion supporting gas through tertiary ports 27. In addition to supporting combustion, the tertiary combustion supporting gas improves lateral distribution of heat across combustion chamber 8. In this regard, no additional flame deflection means are usually required.

Tubes 28 are arranged in upper zone 9 of combustion chamber 8- as best seen in FIGURE H.

- Inflowing combustion supporting gas serves as the cooling means for the heater. The combustion supporting gas is circulated through entrance chamber 16 in counterflow relationship relative the flame in the combustion chamber. As shown in FIGURE I, the combustion supporting gas, here air, enters via filter 29 by means of blowers at 31. Of course, in many environments and applications, filters and blowers would not be necessary. The air enters by way of wind box 30 and entrance ports '32 into entrance chamber 16 to cool inner shell 1 and in so doing to be preheated. Preheating of the air improves combustion and minimizes radiation losses.

Isining 33 acts as a sound absorber for combustion noises.

It will be understood by those skilled in the fired heater engineering that wide changes may be made in the details of the preferred design here presented without departing from the scope of the invention defined in the claims. It should be particularly obviousthat many gases other than air contain appreciable quantities of oxygen and are accordingly capable of supporting combustion. When these gases .occur at temperatures sufficiently low for them to cool inner chamber 1, they are equivalent to air for the practice of this invention.

I claim:

1. A fired heater comprising an upright open ended thin metal inner shell free of a lining and having a low heat storage capacity relative to a refractory wall and having an inlet end and an outlet end and defining a combustion chamber therein, A

the inlet end spaced from the outlet end,

the combustion chamber being divided approximately equally into a lower zone and an upper zone,

an outer shell mounted about the inner shell,

the outer shell spaced from the inner shell to define an entrance chamber embracing the inner shell,

means defining a source of fuel, at least one burner nozzle communicating with the source of fuel and extending into the opening of the inlet end of the inner shell to inject fuel therein,

opening means situated at the inlet end and operatively associated with the burner nozzle for introducing combustion supporting air from the entrance chamber into the combustion chamber,

flue means connected to the inner shell at 'the outlet end for exhausting combustion gases from the combustion chamber so that combustion gases pass from the inlet end toward the outlet end, therethrough,

the outer shell defining at least one entrance port communicating with the entrance chamber adjacent of V the outlet end, blower means for supplying air,

the entrance port communicating with said blower means so that incoming air courses through the entrance chamber from the outlet end toward the opening means situated in the inlet end in counterflow relationship relative the combustion gases in the combustion chamber whereby the inner shell is cooled and the air is preheated,

at least one tube mounted in the combustion chamber and spaced in the upper zone from the burner nozzle toward the outlet end,

means for circulating a fluid through the tube for noncontact heat exchange relationship with combustion gases,

the inner shell defining a plurality of tertiary ports in the lower zone between inlet end and the tube and communicatingthe entrance .chamber with the combustion chamber to, introduce tertiary air thereto and to laterally distribute heat.

2. Afired heater suitable for cryogenic fluids and comprising an upright open-ended elongated thin metal inner shell free of alining and having a low heat storage capacity relative to a refractory wall and having sides and a bottom opening .anddefining a combustion chamber therein divided approximately equally into an upper zone above a lower zone,

the shelllin the lower zone gradually converging toward the bottom opening, 1

an outer shell mounted about the inner shell,

the outer shell having sides and an upper end and .spaced from the inner shell to define an entrance chamber embracing the inner shell,

means defining a source of gaseous fuel, a plurality of burner nozzles communicating with the source of gaseous fuel and extending into the bottom opening of the inner shell to inject fuel into the combustion chamber,

at least one burner block with an inner opening mounted about each of the burner nozzles,

the inner openings communicating in flow series between the entrance chamber and the combustion chamber for introducing combustion supporting air to mix with the fuel,

the burner block spaced from the inner shell to define at least one outer "opening communicating the entrance chamber with the combustion chamber for the admission of additional air to the combustion chamber,

flue means connected to the inner shell and communicating with the upper zone for exhausting combustion gases from the combustion chamber so that combustion gases pass from the lower zone to the upper zone therethrough,

the outer shell defining at least one entrance port in each side adjacent the upper end and communicating with the entrance chamber, blower means for supplying air,

the entrance port communicating with said blower means so that incoming air will be drawn downward through the entrance chamber to the inner opening and the outer opening in counterflow relationship relative the combustion gases in the combustion chamber whereby the inner shell is cooled and the air is preheated,

at least one tube'mounted in the upper zone,

means for circulating a cryogenic fluid through the tube for non-contact heat exchange relationship with combustion gases,

the inner shell defining a plurality of tertiary ports in the lower zone in spaced relationship from the burner block and communicating the entrance chamber with the lower zone to introducetertiary airinto the combustion chamber and to laterally distribute heat.

7 References Cited in the file of this patent UNITED STATES PATENTS Hensel Aug. 15, 1944 

1. A FIRED HEATER COMPRISING AN UPRIGHT OPEN ENDED THIN METAL INNER SHELL FREE OF A LINING AND HAVING A LOW HEAT STORAGE CAPACITY RELATIVE TO A REFRACTORY WALL AND HAVING AN INLET END AND AN OUTLET END AND DEFINING A COMBUSTION CHAMBER THEREIN, THE INLET END SPACED FROM THE OUTLET END, THE COMBUSTION CHAMBER BEING DIVIDED APPROXIMATELY EQUALLY INTO A LOWER ZONE AND AN UPPER ZONE, AN OUTER SHELL MOUNTED ABOUT THE INNER SHELL, THE OUTER SHELL SPACED FROM THE INNER SHELL TO DEFINE AN ENTRANCE CHAMBER EMBRACING THE INNER SHELL, MEANS DEFINING A SOURCE OF FUEL, AT LEAST ONE BURNER NOZZLE COMMUNICATING WITH THE SOURCE OF FUEL AND EXTENDING INTO THE OPENING OF THE INLET END OF THE INNER SHELL TO INJECT FUEL THEREIN, OPENING MEANS SITUATED AT THE INLET END AND OPERATIVELY ASSOCIATED WITH THE BURNER NOZZLE FOR INTRODUCING COMBUSTION SUPPORTING AIR FROM THE ENTRANCE CHAMBER INTO THE COMBUSTION CHAMBER, FLUE MEANS CONNECTED TO THE INNER SHELL AT THE OUTLET END FOR EXHAUSTING COMBUSTION GASES FROM THE COMBUSTION CHAMBER SO THAT COMBUSTION GASES PASS FROM THE INLET END TOWARD THE OUTLET END, THERETHROUGH, THE OUTER SHELL DEFINING AT LEAST ONE ENTRANCE PORT COMMUNICATING WITH THE ENTRANCE CHAMBER ADJACENT OF THE OUTLET END, BLOWER MEANS FOR SUPPLYING AIR, THE ENTRANCE PORT COMMUNICATING WITH SAID BLOWER MEANS SO THAT INCOMING AIR COURSES THROUGH THE ENTRANCE CHAMBER FROM THE OUTLET END TOWARD THE OPENING MEANS SITUATED IN THE INLET END IN COUNTERFLOW RELATIONSHIP RELATIVE THE COMBUSTION GASES IN THE COMBUSTION CHAMBER WHEREBY THE INNER SHELL IS COOLED AND THE AIR IS PREHEATED, AT LEAST ONE TUBE MOUNTED IN THE COMBUSTION CHAMBER AND SPACED IN THE UPPER ZONE FROM THE BURNER NOZZLE TOWARD THE OUTLET END, MEANS FOR CIRCULATING A FLUID THROUGH THE TUBE FOR NONCONTACT HEAT EXCHANGE RELATIONSHIP WITH COMBUSTION GASES, THE INNER SHELL DEFINING A PLURALITY OF TERITARY PORTS IN THE LOWER ZONE BETWEEN INLET END AND THE TUBE AND COMMUNICATING THE ENTRANCE CHAMBER WITH THE COMBUSTION CHAMBER TO INTRODUCE TERTIARY AIR THERETO AND TO LATERALLY DISTRIBUTE HEAT. 